I have one of Eric's chip, 50lb injectors and a upgrade fuel pump.
I checked with my friend that built the motor many years back!!! he did say the motor need to come out... so I really doubt if the head stud has the allen key end.
I have figured if it is bad head gasket or something else. for the last 2 years when I bring the car out from storage, I notice water in the pan... so I drain the pan, put in new oil & GM's rad pill/leak fix. I let it run for a while and drain the pan. The first change over, the oil looks like chocolate milk. I do this a couple of time until the oil looks like oil. I have done 2 oil change since... and no sign of antifreeze or leak. I guess those GM rad pills for... for a season.
I guess over the winter, the antifreeze slowly leaks into the motor. I hope it is head gasket... but I fear the worse.. like a crack block or something. Unfortunately, I don't have garage space to do work!!!!
And now for my next dilemma, my 2009 GMC Sierra is in for a motor rebuild. I thought is was the dreaded bad lifters... but the dealership said something happen to the bottom end.... that is $8000.
dave